The world is throwing away a shocking amount of food. A report last week claimed that at least a third of the 4 billion tonnes of food the world produces each year never gets as far as our mouths. Between 30% and 50% of food purchased in Europe and the US is thrown away. The research is questioned, not least by the supermarkets, but it does echo the results of an exercise in Britain six years ago, when researchers for the government-funded Waste and Resources Action Programme (Wrap) went through the nation's rubbish bins. It concluded that we were throwing away 30% of the food we'd bought while it was still edible.

Britain – and much of the rich world – has got used to filling the fridge with what looks nice, not what it actually needs. The cost of that indulgence is, says the Institute of Mechanical Engineers, £10bn annually. Globally, the cost, in money, energy and ever-scarcer water, is unquantifiable.

Our future food security has been climbing the top 10 of current global worries. The prospect of feeding a mid-century planet of around 9 billion people looks impossible without major and potentially unattractive changes to farming and our diet. If you accept the United Nations Food and Agricultural Organisation's call for production to be increased by 70% to feed the population of 2050, most of the work will be achieved just by being a bit more thrifty. All we have to do is to use better what is already there.

However, throwing food out is easy. Using it sensibly, especially the less attractive bits, is not. The urge to bin and buy again, encouraged by multimillion pound advertising campaigns, is all the less resistible now because, despite recent price rises, for most of us, food is cheap. At Christmas, the average family spent just over £100 on the big meal, a quarter of what it spent on presents. Stopping the waste will take more than a few celebrity chefs telling us how to use the roast chicken leftovers or asking the supermarkets to relax a bit with buy one, get one free offers.

Education of consumers and voluntary agreements with the retail industry have all been tried: Wrap is 13 years old this year and has not impressed. Its critics say that its expensive information campaigns under slogans such as "Love Food Hate Waste" lack targets and convincingly audited results. Like so many toothless quangos, it can only cajole business rather than bring it firmly to heel. More households may be portion-planning and recycling now, because of Wrap's adverts, but the slight reduction in the tonnage of food estimated to have been thrown away in British households (from 8.3m in 2006/07 to 7.2m in 2010) is probably accounted for by the price rises and stall in incomes that followed the global economic crash of 2008.

Here we come to the uncomfortable core of the problem. Price is the key factor in our behaviour with food and food may, simply, be too cheap. Certainly, in Britain it is cheaper than at any time in history: we spend less than 10% of household income on food and drink. In 1950, we spent around 25%. In the developing world, 50% or more of income is spent on food. Tellingly, Britain spends less than any other country in Europe. Worldwide, it seems that the lower a country's food/income ratio, the higher its incidence of obesity. Presumably, the higher also the proportion of food it chucks out.

Observers of food policy certainly believe that cheap food is a problem or, as Professor Tim Lang of City University tells it, that too much of the true cost of food is born not by the consumer or the retailer. The environmental and health damage caused by modern food production and its transport, as well as by excessive consumption, entails vast costs, often picked up by people far away from Tesco's catchments. But it is the supermarkets' eternal price wars – their one-track marketing philosophy where "value" trumps all other qualities in food – that have driven prices so low. Without restoring a sense of the real value of food, how will we stop all but the hungry wasting it?

Food inflation is a key political indicator, yet no government is going to risk price rises for all the good it might do for our health or our environment, let alone the chance of stopping the landfill. Supermarkets, with their powerful lobbying arms and political donations, habitually wriggle away from legislation and Competition Commission criticism merely with the threat that any new regulation will raise prices. That has to stop. A far tougher position is required.

The government's promise to abolish the use of "sell by" and "display until" labels has been parlayed into voluntary Food Standards Agency "advice". Because of industry resistance, Wrap has never fully measured waste caused upstream from the household, even though the retailers and manufacturers are certainly to blame for more of the tonnage that goes to landfill. It may always be easier to blame the consumer but what is required is far stricter regulation of the food giants.

So how could we regulate? Producers complain that the major supermarket chains enslave them in draconian contracts that set up a damaging chain reaction. Producers then pay low wages, which are in turn subsidised by taxpayers via tax credits. These boost incomes that are still so low that families are forced to buy inferior food. (Supermarket chains – hugely profitable – also pay risibly low wages to workers.) Ending this vicious cycle is not simply about food pricing, it's a far larger debate. Even in austerity, the profits of the "big food" companies continue to rise. This is about more than pricing – it's about a sense of responsibility about what's fair.

An alternative to voluntary change is to tax the food industry in just proportion to the damage it causes. Another idea gaining ground across Europe is for a sugar tax – the cheap processed foods and soft drinks that carry the largest profit margins (and which are a key cause of obesity) depend hugely on sugar for their appeal. Food price rises would result and the supermarkets' vast profits might have to take a hit. Those who would really suffer are the poor and their children and that is a challenge to be met fairly with a living wage, not by caps on benefits or food banks.

There are lots of ideas around for the "zero-waste economy" that successive governments have repeatedly promised. But first and foremost, politicians have to conquer their fear of "big food".